Why Single Fire?
Have you ever been caught up in a rush of creative energy while shaping a piece, and lost that feeling while you waited for the piece to dry and then be bisque fired?
When you look at the bisqued piece, does in seem lifeless and divorced from when you were shaping it? Does it feel like glazing is some totally separate process that is very
difficult to unify with the forming process?
Do you hate the way bisqueware sucks the liquid out of your glazes, making runs and drips twice as thick as the rest of the glaze coating? And when you do brushwork does this sucking property thwart your attempts at carefully controlled strokes?
Do your high clay content glazes shrink and crack on bisqueware and then crawl away from the cracks in the firing?
Do you love the feel and control of painting with acrylics or oils where your paint glides off the brush and mixes predictably with previous strokes?
Would you like to compress your production cycle into half your usual time?
Would you like to use about a third less energy in firing your kiln?
Would you like to cut your kiln loading and unloading in half, while still producing the same amount of finished work?
The more of those questions to which you answered "Yes", the more reasons for you to look into single firing.
If we can get a committed group together to study the single fire process somewhat systematically, we will likely progress much faster than if we work individually in isolation. With a dedicated group we would also have a better chance of enlisting the aid of one or more established experts.
- For a preview of why you might want to do something so radical, see "http://www.centerstreetclay.com/Site/ElectricGlazeFiring_4.html">the electric glaze firing page at centerstreetclay.com Steven Hill's Website. He has been single firing for some thirty years.
- Basically, single firing involves glazing your pieces when they are in the leather hard to bone dry stage. You need to use high clay content glazes that will shrink similarly to the clay body to which they are applied as both the body and glaze dry out. Firing has to be very slow in the initial phases to allow moisture to escape slowly from the body and through the glaze without separating the two. After the unbound water and the water of crystalization are driven off, the rest of the firing cycle can proceed pretty normally for the glaze effects you are trying to achieve.
- Single firing is not some Johnnie-Come-Lately, hare-brained invention. It has been used commercially for many years, glazed bricks, roof, floor, and wall tiles, toilets, and ceramic plumbing fixtures are all typically single fired.
Here are some links to photographs of single fired pottery.
- These are gorgeous pots by Gertrude Graham Smith. They were salt fired to cone 10, so we won't be able to duplicate this look in our cone 6 oxidation firing. This is just a sampling of possibilities.
- I received an email from Ellen Fisher as to her firing range, and she's doing low fire terra cotta single firing with commercial low-fire glazes. So the technique is valid across all clay firing temperatures.
If you are ready to dive in then you'll need some techniques. You won't be able to use those glazing tongs on leather hard clay or on greenware.
- Richard Aerni had an article on single firing in the Dec 94 issue of Ceramics Monthly which you can read at his "http://www.richardaerni.com/cm94.html">Website. He's talking about ash glazes reduction fired to cone 10, but his discussion of glaze mixing, combinations, and spray application apply equally to our work at cone 6 in oxidation.
An Obvious Combination for Single Firing
would be to paint a leatherhard piece with colored slips, and then glaze it with a suitable clear single fire glaze. I haven't found a lot of ^6 raw glazes, but here are a couple quoted from the clayart listserve.
Marek & Pauline Drzazga-Donaldson on fri 10 mar 00
I have developed a once fire cone 6 glaze from the basic Leach cone
10 - 11 glaze.
Cone 6 Based on Leach Clear/Transparent Oxidised
Potash Feldspar 40
Flint (Quartz) 25
Whiting (CaCo3) 20
China Clay 12.5
This gives a really good shiny surface and can be quite thick and
does not run. You could add 2.5 of Bentonite to make it up to
Cone 6 Raw or Once Fired Glaze. This glaze can be painted on very
Potash Feldspar 38
Flint (Quartz) 20
Whiting (Chalk) 32
Ball Clay 10
This glaze acts in similar manner to the first. Can be applied
thick, takes oxides well, very stable over a wide range, does not
run. If this one works for you let me know. It really is a
stallwart for me.If you give it a really good cone 6 -7 then it
will pool nicely. Happy potting Marek "http://www.moley.uk.com">http://www.moley.uk.com